In sausage production, a finely divided meat composition, commonly referred to as an emulsion, is stuffed into a tubular casing. For automatic operation, these tubular casings are utilized in shirred lengths known to persons familiar with the art as "sticks". After a stick is loaded onto the stuffing machine it is intended that the stuffing machine run continuously until the casing supply is exhausted. In this fashion, a plurality of stuffed products or "logs" are produced from the casing in each shirred stick. The length of each log may vary from 2 to 6 feet or more. The stuffed log is then cooked or cured by well known processes to produce a processed sausage meat for consumption.
For aesthetic, economic and quality control considerations, it is desirable for the processed log to have a substantially uniform diameter over its entire length.
For example, a substantially uniform diameter is especially desired for the production of stuffed products which are subsequently sliced and prepackaged for retail sales. Machines which slice these products usually are set up to cut a predetermined number of slices for each package, but at retail the packages are sold on a weight basis. Accordingly, it is important to have a substantially uniform diameter so that the predetermined slice count will consistently produce packages of substantially the same weight. To achieve a desired processed diameter when using a cellulosic casing, it is customary to stuff to a "green" or unprocessed diameter slightly larger than the desired processed diameter to accommodate for shrinkage which occurs during processing.
Stuffing machines for producing logs of substantially constant diameter are well known. For example in U.S. Pat. No. Re. 30,390, a stuffing machine is disclosed which uses a sizing disc within the casing to circumferentially stretch the casing just prior to stuffing. This circumferential stretch exerts a drag or "holdback" on the casing. This drag (sometimes referred to herein as "holdback") resists the forward movement of the casing as a food product is introduced under pressure into the casing. This insures that the casing stuffs out to the full diameter recommended by the casing manufacturer.
Due to casing manufacturing tolerances, the diameter of a casing may vary slightly along its length. To some extent, the sizing disc as disclosed in U.S. Pat. No. Re. 30,390 compensates for this variation in casing diameter so the filled diameter is substantially constant. For example, if the casing diameter decreases, the holdback or drag force increases as the narrowed section of casing passes over the fixed circumference of the sizing disc. The increased drag slows the passage of casing so its stuffed diameter increases. Conversely, if the casing diameter increases, the casing passes more freely over the disc so the stuffed diameter decreases. The result is a stuffed product having a substantially constant diameter. In order to obtain this effect, the diameter of the sizing disc should be the same as the recommended stuffed diameter of the casing. Thus, in use, a sizing disc of a given size only is used with one size of casing.
When using a sizing disc, stuffed diameter is further controlled by positioning a pressure ring adjacent the sizing disc as disclosed in U.S. Pat. No. 4,077,090. The pressure ring is disposed on the outside of the casing so the casing passes first over the sizing disc and then inward through the pressure ring. Changing the longitudinal distance between the sizing disc and pressure ring is a known way of adjusting the drag on the casing. For example, U.S. Pat. No. 4,766,645 discloses a stuffing machine having sensors which monitor the diameter of the casing as it is stuffed. These sensors are capable of generating feedback signals for automatically adjusting the longitudinal distance between the sizing disc and pressure ring to adjust the holdback on the casing as needed to maintain a desired stuffed diameter.
One problem which has been experienced during the processing of a green log is that the first-stuffed leading end portion of the green log tends to undergo a larger diameter reduction than the rest of the log. Thus, even though the green log is stuffed to a uniform diameter over substantially its full length, the leading end portion of stuffed length after processing will have a smaller diameter than the remainder of the processed log. This is sometimes referred to as "front-end slump" and effects about the first 2-8 inches of stuffed length. Front-end slump is particularly troubling when making a log for slicing. This is because with front-end slump, a greater number of slices must be discarded as undersize compared to a processed log of uniform diameter over substantially its entire length.
For example, it generally is appreciated that a green log about 4.5 inches in diameter comprising a high quality meat emulsion as is used for bologna, will shrink diametrically about 2% during processing. This is about 0.1 inch for the green log 4.5 inches in diameter. However, shrinkage of the leading or first end portion of the log is closer to 4% or 0.2 inch for the same green diameter of 4.5 inches.
One method proposed to insure a uniform diameter over substantially the entire length of the processed log, is to over stuff the front end portion of the green log to compensate for the greater shrinkage during processing.
However, the increased drag required to over stuff the leading end of a stuffed product may present problems. For example, if the drag is too great at the onset of stuffing the casing may break under the strain. It also is possible for the closure at, the leading end to fail resulting in what is referred to as a "blown end". These problems are particularly acute when the appropriate drag is produced by positioning the sizing disc and pressure ring one against the other so the casing is pinched therebetween. If the casing is pinched between the sizing disc and pressure ring at the onset of stuffing, maximum strain is produced on the casing and closure due to the high static friction which must be overcome to start the casing moving between the pressed together sizing disc and pressure ring.
Accordingly, it is an object of the present invention to provide a stuffing method and apparatus for producing a stuffed log having a leading, first-stuffed end portion which is larger in diameter than the remaining portion of the log.
Another object of the present invention is to provide a stuffing method and apparatus which exerts a higher drag force on the casing while stuffing a leading end portion of the log and then lowers drag for stuffing the remainder of the log.
Still another object of the invention is to provide a stuffing method and apparatus which applies a lower drag force on the casing at the onset of stuffing and then immediately increases the drag force to a higher level for stuffing a leading end portion of the casing